Wireless communication method for allocating clear channel, and wireless communication terminal using same

ABSTRACT

The present invention relates to a wireless communication method for clear channel assessment and a wireless communication terminal using the same, and more particularly, to a wireless communication method and a wireless communication terminal for performing efficient clear channel assessment based on BBS identifier information of non-legacy wireless LAN information. To this end, provided is a wireless communication method including: receiving a radio signal of a specific channel; measuring a signal strength of the received radio signal; and determining whether the specific channel is busy based on the measured signal strength and BSS identifier information of the radio signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of International PatentApplication No. PCT/KR2015/004763 filed on May 12, 2015, which claimspriority to Korean Patent Application Nos. 10-2014-0056995 filed on May13, 2014, 10-2014-0088218 filed on Jul. 14, 2014, 10-20140089400 filedon Jul. 15, 2014 and 10-2014-0170812 filed on Dec. 2, 2014, thedisclosures of which are hereby incorporated in their entireties byreference.

TECHNICAL FIELD

The present invention relates to a wireless communication method forclear channel assessment and a wireless communication terminal using thesame, and more particularly, to a wireless communication method and awireless communication terminal for performing efficient clear channelassessment based on BSS identifier information of non-legacy wirelessLAN information.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelessLAN technology that can provide a rapid wireless Internet service to themobile apparatuses has been significantly spotlighted. The wireless LANtechnology allows mobile apparatuses including a smart phone, a smartpad, a laptop computer, a portable multimedia player, an embeddedapparatus, and the like to wirelessly access the Internet in home or acompany or a specific service providing area based on a wirelesscommunication technology in a short range.

Institute of Electrical and Electronics Engineers (IEEE) 802.11 hascommercialized or developed various technological standards since aninitial wireless LAN technology is supported using a frequency of 2.4GHz. First, the IEEE 802.11b supports a communication speed of a maximumof 11 Mbps while using a frequency of a 2.4 GHz band. IEEE 802.11a whichis commercialized after the IEEE 802.11b uses a frequency of not the 2.4GHz band but a 5 GHz band to reduce an influence by interference ascompared with the frequency of the 2.4 GHz band which is significantlycongested and improves the communication speed up to a maximum of 54Mbps by using an OFDM technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequency of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n is provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n comes intothe spotlight. Among them, IEEE 802.11ac supports a wide bandwidth (80to 160 MHz) in the 5 GHz frequency. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven an operation in the 2.4 GHz band for the backward compatibilitywith the existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of a radiointerface accepted by 802.11n, such as a wider radio frequency bandwidth(a maximum of 160 MHz), more MIMO spatial streams (a maximum of 8),multi-user MIMO, and high-density modulation (a maximum of 256 QAM).Further, as a scheme that transmits data by using a 60 GHz band insteadof the existing 2.4 GHz/5 GHz, IEEE 802.11ad is provided. The IEEE802.11ad as a transmission standard that provides a speed of a maximumof 7 Gbps by using a beamforming technology is suitable for high bitrate moving picture streaming such as massive data or non-compression HDvideo. However, since it is difficult for the 60 GHz frequency band topass through an obstacle, it is disadvantageous in that the 60 GHzfrequency band can be used only among devices in a short-distance space.

Meanwhile, in recent years, as next-generation wireless LAN standardsafter the 802.11ac and 802.11ad, discussion for providing ahigh-efficiency and high-performance wireless LAN communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless LAN environment, communication havinghigh frequency efficiency needs to be provided indoors/outdoors underthe presence of high-density stations and access points (APs) andvarious technologies for implementing the communication are required.

DISCLOSURE Technical Problem

As described above, an object of the present invention is to providehigh-efficiency/high-performance wireless LAN communication in ahigh-density environment.

In particular, an object of the present invention is to provide a methodthat can effectively transmit data in an overlapped basic service set(BSS) environment.

Further, an object of the present invention is to increase atransmission opportunity and transmission rate of data by providing anefficient spatial reuse method in the overlapped BSS environment.

Technical Solution

In order to achieve the objects, the present invention provides awireless communication method and a wireless communication terminal asbelow.

First, the present invention provides a wireless communication method ofa terminal including: receiving a radio signal of a specific channel;measuring a signal strength of the received radio signal; anddetermining whether the specific channel is busy based on the measuredsignal strength and BSS identifier information of the radio signal.

In this case, the determining may be performed based on clear channelassessment (CCA) for the specific channel, and a CCA threshold used forthe CCA may be set to different levels according to whether the BSSidentifier information of the radio signal is the same as BSS identifierinformation of the terminal.

Further, when the BSS identifier information of the radio signal is thesame as BSS identifier information of the terminal, a first CCAthreshold may be used for the CCA and when the BSS identifierinformation of the radio signal is different from BSS identifierinformation of the terminal, a second CCA threshold having a higherlevel than the first CCA threshold may be used for the CCA.

In addition, the wireless communication method may further includeobtaining at least one of legacy wireless LAN information and non-legacywireless LAN information by using preamble information of the receivedradio signal, wherein in the determining, when the non-legacy wirelessLAN information is obtained from the radio signal, whether the specificchannel is busy may be determined based on the BSS identifierinformation of the radio signal.

Next, the present invention provides a wireless communication method ofa terminal including: receiving a radio signal of a specific channel;measuring a signal strength of the received radio signal; obtaining atleast one of legacy wireless LAN information and non-legacy wireless LANinformation by using preamble information of the received radio signal;and determining whether the specific channel is busy based on BSSidentifier information of the radio signal when the measured signalstrength is between a first clear channel assessment (CCA) threshold anda second CCA threshold and the non-legacy wireless LAN information isobtained from the radio signal.

In this case, the BSS identifier information of the radio signal mayrepresent abbreviated information of a BSS identifier for the radiosignal.

According to the embodiment of the present invention, in thedetermining, whether the specific channel is busy may be determinedbased on a result of comparing the BSS identifier information of theradio signal and the BSS identifier information of the terminal.

In this case, in the determining, when the BSS identifier information ofthe radio signal is different from the BSS identifier information of theterminal, it may be determined that the specific channel is in an idlestate.

Further, in the determining, when the BSS identifier information of theradio signal is the same as the BSS identifier information of theterminal, it may be determined that the specific channel is in a busystate.

According to an embodiment of the present invention, the radio signalmay include a first preamble for a legacy terminal and a second preamblefor a non-legacy terminal, and the BSS identifier information of theradio signal may be extracted from the second preamble of the radiosignal.

According to another embodiment of the present invention, the radiosignal may be configured to include the first preamble for the legacyterminal and the second preamble for the non-legacy terminal and thefirst preamble may be configured to at least include a first subcarrierset for the legacy terminal, and when the first preamble is configuredto additionally include a second subcarrier set different from the firstsubcarrier set, the non-legacy wireless LAN information may be obtainedfrom the second subcarrier set.

In this case, the BSS identifier information of the received radiosignal may be extracted from information on the second subcarrier set ofthe first preamble.

According to yet another embodiment of the present invention, the radiosignal may include the first preamble for the legacy terminal and thesecond preamble for the non-legacy terminal, and whether the radiosignal includes the non-legacy wireless LAN information is determinedbased on information on predetermined bits of the first preamble.

According to an embodiment of the present invention, the radio signalmay include the first preamble for the legacy terminal and the secondpreamble for the non-legacy terminal, and the BSS identifier informationof the radio signal may be extracted from the predetermined bit field ofthe first preamble.

In this case, a predetermined bit of the predetermined bit field mayrepresent whether the radio signal includes the non-legacy wireless LANinformation, and when the predetermined bit represents that the radiosignal includes the non-legacy wireless LAN information, the BSSidentifier information of the radio signal may be extracted from thepredetermined bit field.

According to another embodiment of the present invention, the firstpreamble may be configured to at least include the first subcarrier setfor the legacy terminal, and when the first preamble is configured toadditionally include the second subcarrier set different from the firstsubcarrier set, the BSS identifier information of the radio signal maybe extracted from the predetermined bit field.

Next, the present invention provides, as a wireless communicationmethod, a wireless communication method including: receiving a radiosignal of a specific channel; measuring a signal strength of thereceived radio signal; extracting BSS configuration information from theradio signal; and determining whether the specific channel is busy basedon the measured signal strength and the BSS configuration information ofthe radio signal.

In this case, the determining may be performed based on clear channelassessment (CCA) for the specific channel, and a CCA threshold used forthe CCA may be decided based on the BSS configuration information of theradio signal.

According to the embodiment of the present invention the BSSconfiguration information may include at least one of channelinformation, bandwidth information and communication scheme informationused in the corresponding BSS.

According to an embodiment, the CCA threshold when the channelinformation of the received radio signal is different from the channelinformation of the BSS to which the terminal belongs may be set to ahigher level than the CCA threshold when the channel information is thesame as each other.

Further, the CCA threshold when the channel information of the receivedradio signal and the channel information of the BSS to which theterminal belongs to represents that both channels are adjacent to eachother may be set to a higher level than the CCA threshold when thechannel information represents that both channels are not adjacent toeach other.

According to another embodiment, the CCA threshold may be increased whenthe channel information of the received radio signal and the channelinformation of the BSS to which the corresponding terminal belongs areadjacent to each other and the CCA threshold increment amount maydecrease as the bandwidth of the received radio signal is larger.

According to an embodiment of the present invention, the radio signalmay include a first preamble for a legacy terminal and a second preamblefor a non-legacy terminal, and the BSS configuration information of theradio signal may be extracted from the second preamble of the radiosignal.

According to an embodiment of the present invention, the radio signalmay include the first preamble for the legacy terminal and the secondpreamble for the non-legacy terminal, and the BSS configurationinformation of the radio signal may be extracted from the predeterminedbit field of the first preamble.

In this case, a predetermined bit of the predetermined bit field mayrepresent whether the radio signal includes the non-legacy wireless LANinformation, and when the predetermined bit represents that the radiosignal includes the non-legacy wireless LAN information, the BSSconfiguration information of the radio signal may be extracted from thepredetermined bit field.

According to yet another embodiment of the present invention, the firstpreamble may be configured to at least include the first subcarrier setfor the legacy terminal, and when the first preamble is configured toadditionally include the second subcarrier set different from the firstsubcarrier set, the BSS configuration information of the radio signalmay be extracted from the predetermined bit field.

Next, the present invention provides a wireless communication terminalincluding: a transceiver transmitting and receiving a radio signal; anda processor controlling an operation of the terminal, wherein theprocessor measures a signal strength of a radio signal of a specificchannel, which is received through the transceiver, and determineswhether the specific channel is busy based on the measured signalstrength and BSS identifier information of the radio signal.

In this case, the processor may obtain at least one of legacy wirelessLAN information and non-legacy wireless LAN information by usingpreamble information of the received radio signal, and determine, whenthe non-legacy wireless LAN information is obtained from the radiosignal, whether the specific channel is busy based on the BSS identifierinformation of the radio signal.

Further, the processor may perform the determination based on clearchannel assessment (CCA) for the specific channel, and a CCA thresholdused for the CCA may be set to different levels according to whether theBSS identifier information of the radio signal is the same as BSSidentifier information of the terminal.

Next, the present invention provides a wireless communication terminalincluding: a transceiver transmitting and receiving a radio signal; anda processor controlling an operation of the terminal, wherein theprocessor measures a signal strength of the radio signal receivedthrough the transceiver; obtains at least one of legacy wireless LANinformation and non-legacy wireless LAN information by using preambleinformation of the received radio signal; and determines whether thespecific channel is busy based on BSS identifier information of theradio signal when the measured signal strength is between a first clearchannel assessment (CCA) threshold and a second CCA threshold and thenon-legacy wireless LAN information is obtained from the radio signal.

Next, the present invention provides a wireless communication terminalincluding: a transceiver transmitting and receiving a radio signal; anda processor controlling an operation of the terminal, wherein theprocessor measures a signal strength of a radio signal of a specificchannel, which is received through the transceiver; extracts BSSconfiguration information from the radio signal; and determines whetherthe specific channel is busy based on the measured signal strength andthe BSS configuration information of the radio signal.

Advantageous Effects

According to embodiments of the present invention, it can be efficientlydetermined whether a radio signal received in an overlapped BSSenvironment is a wireless LAN signal of the same BSS and whether toadaptively use the corresponding channel can be decided based on thedetermination.

Further, according to an embodiment of the present invention, when thereceived radio signal is a legacy wireless LAN signal from which BSSidentifier information is not extracted, whether the channel is in abusy state is determined according to a received signal strength of thecorresponding signal in a lump to minimize a time delay required toadditionally determine a BSS identifier of the legacy wireless LANsignal during a CCA process.

Further, according to another embodiment of the present invention, whena wireless LAN signal having the same BSS identifier information as thatof a terminal is received, an inequity problem in which different CCAthreshold values are applied according to whether the correspondingwireless LAN signal includes non-legacy wireless LAN information can beresolved. That is, CCA threshold values for a legacy signal and anon-legacy signal are similarly applied to the wireless LAN signalhaving the same BSS identifier information as that of the terminal tomaintain equity for channel occupation between a legacy terminal and anon-legacy terminal.

According to yet another embodiment of the present invention, since atleast some of non-legacy wireless LAN information such as the BSSidentifier information can be obtained from a legacy preamble beforechecking a non-legacy preamble, CCA may be performed within a shortertime.

According to still yet another embodiment of the present invention, whenan interference signal generated by spurious of an adjacent channel isreceived by the terminal, communication between adjacent channels canefficiently controlled by adjusting the CCA threshold value tocorrespond to the relevant interference signal.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention.

FIG. 2 is a diagram illustrating a wireless LAN system according toanother embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a stationaccording to an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a carrier sense multiple access(CSMA)/collision avoidance (CA) method used in wireless LANcommunication.

FIG. 6 is a diagram illustrating one embodiment of a wirelesscommunication scheme using a CCA technique.

FIG. 7 is a diagram illustrating one example of an overlapped BSSenvironment.

FIGS. 8 to 10 are diagrams illustrating various embodiments of a CCAmethod using BSS identifier information of a received radio signal.

FIGS. 11 to 13 are diagrams illustrating another embodiment of a CCAmethod using whether to obtain non-legacy wireless LAN information froma received radio signal and BSS identifier information.

FIG. 14 is a diagram illustrating a frame structure of a wireless LANsignal according to an embodiment of the present invention.

FIG. 15 is a diagram illustrating a method for representing BSSidentifier information according to an embodiment of the presentinvention.

FIG. 16 is a diagram illustrating an embodiment of a subcarrierconfiguration used in a legacy preamble of a wireless LAN signal.

FIG. 17 is a diagram illustrating an embodiment of a subcarrierconfiguration used in a non-legacy wireless LAN signal.

FIG. 18 is a diagram illustrating a method for representing non-legacywireless LAN information by using a predetermined bit field of thelegacy preamble.

FIG. 19 is a diagram illustrating an embodiment of a method forperforming communication by additionally using BSS configurationinformation.

BEST MODE

Terms used in the specification adopt general terms which are currentlywidely used by considering functions in the present invention, but theterms may be changed depending on an intention of those skilled in theart, customs, and emergence of new technology. Further, in a specificcase, there is a term arbitrarily selected by an applicant and in thiscase, a meaning thereof will be described in a corresponding descriptionpart of the invention. Accordingly, it should be revealed that a termused in the specification should be analyzed based on not just a name ofthe term but a substantial meaning of the term and contents throughoutthe specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “coupled” to another element, the elementmay be “directly coupled” to the other element or “electrically coupled”to the other element through a third element. Further, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising”, will be understood to imply the inclusionof stated elements but not the exclusion of any other elements.Moreover, limitations such as “or more” or “or less” based on a specificthreshold may be appropriately substituted with “more than” or “lessthan”, respectively.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2014-0056995, 10-2014-0088218, 10-2014-0089400, and10-2014-0170812 filed in the Korean Intellectual Property Office and theembodiments and mentioned items described in the respective applicationsare included in the Detailed Description of the present application.

FIG. 1 is a diagram illustrating a wireless LAN system according to anembodiment of the present invention. The wireless LAN system includesone or more basic service sets (BSS) and the BSS represents a set ofapparatuses which are successfully synchronized with each other tocommunicate with each other. In general, the BSS may be classified intoan infrastructure BSS and an independent BSS (IBSS) and FIG. 1illustrates the infrastructure BSS of them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA-1, STA-2, STA-3, STA-4, and STA-5,access points PCP/AP-1 and PCP/AP-2 which are stations providing adistribution service, and a distribution system (DS) connecting themultiple access points PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a radio medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, as a concept including allwireless LAN communication devices such as the station and the AP, aterm ‘terminal’ may be used. A station for wireless communicationincludes a processor and a transceiver and according to the embodiment,may further include a user interface unit and a display unit. Theprocessor may generate a frame to be transmitted through a wirelessnetwork or process a frame received through the wireless network andbesides, perform various processing for controlling the station. Inaddition, the transceiver is functionally connected with the processorand transmits and receives the frame through the wireless network forthe station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via the wireless medium for the stationassociated therewith. In the infrastructure BSS, communication amongnon-AP stations is, in principle, performed via the AP, but when adirect link is configured, direct communication is enabled even amongthe non-AP stations. Meanwhile, in the present invention, the AP is usedas a concept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

The plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, the plurality ofBSSs connected through the distribution system is referred to as anextended service set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless LAN systemaccording to another embodiment of the present invention. In theembodiment of FIG. 2, duplicative description of parts, which are thesame as or correspond to the embodiment of FIG. 1, will be omitted.

Since a BSS-3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA-6 and STA-7 are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA-6 and STA-7 may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a radio signal such asa wireless LAN packet, or the like and may be embedded in the station100 or provided as an exterior. According to the embodiment, thetransceiver 120 may include at least one transmit/receive module usingdifferent frequency bands. That is to say, the transceiver 120 mayinclude transmit/receive modules having different frequency bands suchas 2.4 GHz, 5 GHz, and 60 GHz. According to an embodiment, the station100 may include a transmit/receive module using a frequency band of 6GHz or more and a transmit/receive module using a frequency band of 6GHz or less. The respective transmit/receive modules may performwireless communication with the AP or an external station according to awireless LAN standard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 120 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the station 100. When the station 100 includes aplurality of transmit/receive modules, each transmit/receive module maybe implemented by independent elements or otherwise the plurality ofmodules may be integrated into one chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, that is to say, the transceiver 120,and the like. The processor 110 controls various operations of radiosignal transmission/reception of the station 100 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. That is to say, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, that is to say, the user interface unit 140 and thedisplay unit 150 may be selectively provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may further include a plurality oftransmit/receive modules using different frequency bands. That is, theAP 200 according to the embodiment of the present invention may togetherinclude two or more transmit/receive modules among different frequencybands, that is to say, 2.4 GHz, 5 GHz, and 60 GHz. Preferably, the AP200 may include a transmit/receive module using a frequency band of 6GHz or more and a transmit/receive module using a frequency band of 6GHz or less. The respective transmit/receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the correspondingtransmit/receive module. The transceiver 220 may operate only onetransmit/receive module at a time or simultaneously operate multipletransmit/receive modules together according to the performance andrequirements of the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 controls variousoperations such as radio signal transmission/reception of the AP 200according to the embodiment of the present invention. A detailedembodiment thereof will be described below.

FIG. 5 is a diagram illustrating a carrier sense multiple access(CSMA)/collision avoidance (CA) method used in wireless LANcommunication.

The terminal that performs the wireless LAN communication checks whethera channel is busy by performing carrier sensing before transmittingdata. When a radio signal having a predetermined strength or more issensed, it is determined that the corresponding channel is busy and theterminal delays the access to the corresponding channel. Such a processis referred to as clear channel assessment (CCA) and a level to decidewhether the corresponding signal is sensed is referred to as a CCAthreshold. When a radio signal having the CCA threshold or more, whichis received by the terminal, indicates the corresponding terminal as areceiver, the terminal processes the received radio signal. Meanwhile,when the radio signal is not sensed in the corresponding channel or aradio signal having a strength smaller than the CCA threshold is sensed,it is determined that the channel is idle.

When it is determined that the channel is idle, each terminal havingdata to be transmitted performs a backoff procedure after a time of aninterframe space (IFS) depending on a situation of each terminal, forinstance, an arbitration IFS (AIFS), a PCF IFS (PIFS), or the likeelapses. According to the embodiment, the AIFS may be used as acomponent which substitutes for the existing DCF IFS (DIFS). That is,each terminal stands by while decreasing a slot time as long as a randomnumber allocated to the corresponding terminal during an interval of anidle state of the channel and a terminal that completely exhausts theslot time attempts to access the corresponding channel. As such, aninterval in which each terminal performs the backoff procedure isreferred to as a contention window interval.

When a specific terminal successfully accesses the channel, thecorresponding terminal may transmit data through the channel. However,when the terminal which attempts the access collides with anotherterminal, the terminals which collide with each other are allocated withnew random numbers, respectively to perform the backoff procedure again.According to an embodiment, a random number newly allocated to eachterminal may be decided within a range which is twice larger than arange of a random number which the corresponding terminal is previouslyallocated with. Meanwhile, each terminal attempts the access byperforming the backoff procedure again in a next contention windowinterval and in this case, each terminal performs the backoff procedurefrom a slot time which remains in the previous contention windowinterval. By such a method, the respective terminals that perform thewireless LAN communication may avoid a mutual collision for a specificchannel.

FIG. 6 is a diagram illustrating one embodiment of a wirelesscommunication scheme using a CCA technique.

In wireless communication, for instance, the wireless LAN communication,whether the channel is busy may be sensed through the CCA. In this case,the CCA methods including a signal detection (SD) method, an energydetection (ED) method, a correlation detection (CD) method, and the likemay be used.

First, the signal detection (CCA-SD) is a method that measures a signalstrength of a preamble of a wireless LAN (that is, 802.11) frame. Thismethod may stably detect the signal, but is disadvantageous in that themethod operates only in an initial part of a frame where the preamble ispresent. According to an embodiment, the signal detection may be used inthe CCA for a primary channel in a wideband wireless LAN. Next, theenergy detection (CCA-ED) is a method that senses energy of all signalsreceived with a specific threshold or more. This method may be used tosense a radio signal in which the preamble is not normally sensed, forinstance, signals such as Bluetooth, ZigBee, and the like. Further, themethod may be used in the CCA for a secondary channel in which thesignal is not continuously tracked. Meanwhile, the correlation detection(CCA-CD) as a method that may sense a signal level even in the middle ofa wireless LAN frame uses that a wireless LAN signal has a periodicrepetition pattern of orthogonal frequency division multiplex (OFDM)signal. That is, the correlation detection method receives wireless LANdata for a predetermined time and thereafter, detects signal strengthsof the repetition patterns of an OFDM signal symbol.

According to the embodiment of the present invention, the access of theterminal to the channel may be controlled by using a predetermined CCAthreshold for each CCA method. In the embodiment of FIG. 6, a CCA-EDthreshold 10 represents a predetermined threshold in order to performthe energy detection and a CCA-SD threshold 30 represents apredetermined threshold in order to perform the signal detection.Further, receiving (RX) sensitivity 50 represents a minimum signalstrength at which the terminal may decode the radio signal. According tothe embodiment, the RX sensitivity 50 may be set to a level which is thesame as or lower than the CCA-SD threshold 30 according to a capabilityand a configuration of the terminal. Further, the CCA-ED threshold 10may be set to a higher level than the CCA-SD threshold 30. For example,the CCA-ED threshold 10 and the CCA-SD threshold 30 may be set to −62dBm and −82 dBm, respectively. However, the present invention is notlimited thereto and the CCA-ED threshold 10 and the CCA-SD threshold 30may be differently set according to whether the CCA-ED threshold 10 andthe CCA-SD threshold 30 are thresholds for the primary channel, abandwidth of a channel that performs the CCA, and the like.

According to the embodiment of FIG. 6, each terminal measures a receivedsignal strength indicator (RX RSSI) of the received radio signal anddetermines a channel state based on a comparison between the measuredreceived signal strength and each set CCA threshold.

First, when a radio signal 350 above the RX sensitivity 50, which isreceived in a specific channel has an RX RSSI of the CCA-SD threshold 30or less, it is determined that the corresponding channel is idle.Therefore, the received signal is not processed or protected in theterminal and each terminal may attempt the access to the correspondingchannel according to the method described in FIG. 5, and the like.

When a wireless LAN signal 330 having the RX RSSI of the CCA-SDthreshold 30 or more is received in a specific channel, it is determinedthat the corresponding channel is in a busy state. Accordingly, theterminal that receives the corresponding signal delays the access to thechannel. According to an embodiment, the terminal may determine whetherthe corresponding signal is the wireless LAN signal by using a signalpattern of a preamble part of the received radio signal. According tothe embodiment of FIG. 6, even in case that a wireless LAN signal ofanother BSS is received in addition to a wireless LAN signal of BSSwhich is the same with the corresponding terminal, each terminaldetermines that the channel is in the busy state.

Meanwhile, when a radio signal 310 having the RX RSSI of the CCA-EDthreshold 10 or more is received in a specific channel, it is determinedthat the corresponding channel is in the busy state. In case thatanother type of radio signal (other than the wireless LAN signal) isreceived as well, the terminal determines that the corresponding channelis in the busy state, if the RX RSSI of the corresponding signal is theCCA-ED threshold 10 or more. Accordingly, the terminal that receives thecorresponding signal delays the access to the channel.

FIG. 7 illustrates one example of an overlapping BSS (OBSS) environment.In FIG. 7, in BSS-1 operated by AP-1, station 1 (STA-1) and station 2(STA-2) are associated with AP-1 and in BSS-2 operated by AP-2, station3 (STA-3) and station 4 (STA-4) are associated with AP-2. In theoverlapping BSS environment of FIG. 7, communication coverages of BSS-1and BSS-2 at least partially overlap with each other.

As illustrated in FIG. 7, when STA-3 transmits upload data to AP-2,STA-3 may continuously interfere with STA-2 of BSS-1 positioned adjacentthereto. In this case, interference which occurs while BSS-1 and BSS-2use the same frequency band (for example, 2.4 GHz, 5 GHz, or the like)and the same primary channel is referred to as co-channel interference(CCI). Further, interference which occurs while BSS-1 and BSS-2 use anadjacent primary channel is referred to as adjacent channel interference(ACI). The CCI or ACI may be received with a higher signal strength thanthe CCA threshold (e.g. CCA SD threshold) of STA-2 according to adistance between STA-2 and STA-3. When the interference is received bySTA-2 with the higher strength than the CCA threshold, STA-2 recognizesthat the corresponding channel is in the busy state to delaytransmission of the upload data to AP-1. However, since STA-2 and STA-3are stations that belong to different BSSs, when the CCA threshold ofSTA-2 increases, STA-2 and STA-3 may simultaneously upload to AP-1 andAP-2, respectively, thereby achieving an effect of spatial reuse.

Meanwhile, in FIG. 7, the transmission of the upload data by STA-3 inBSS-2 interferes even in STA-4 that belongs to the same BSS-2. In thiscase, when the CCA threshold of STA-4 increases similarly to STA-2,STA-3 and STA-4 that belong to the same BSS simultaneously transmit theupload data to AP-2, and as a result, a collision may occur. Therefore,in order to increase the CCA threshold for predetermined interference,it is needed to determine whether the corresponding interference iscaused by signals that belong to the same BSS or signals that belong todifferent BSSs. To this end, each terminal needs to verify a BSSidentifier of the received wireless LAN signal or other types ofinformation to distinguish the BSS. Further, it is preferable that theBSS information is verified within a short time while the CCA process isperformed.

FIGS. 8 to 13 are diagrams illustrating various embodiments of the CCAmethod according to the present invention. In the embodiments of FIGS. 8to 13, an area marked with a shade indicates a radio signal which isreceived but disregarded, that is, not protected by the terminal. Inother words, when the radio signal corresponding to the area marked withthe shade is received, the terminal determines that the correspondingchannel is in the idle state. Meanwhile, when a radio signalcorresponding to an area not marked with the shade is received, theterminal determines that the corresponding channel is in the busy state.In this case, the RX sensitivity may be set to the level which is thesame as or lower than the CCA-SD threshold according to the capabilityand the configuration of the terminal. Further, the CCA-ED threshold maybe set to the higher level than the CCA-SD threshold. Individualprocesses described in FIG. 5 may be performed based on a result ofdetermining whether the channel is busy in each embodiment to bedescribed below.

In each of the embodiments of FIGS. 8 to 10, the terminal may measurethe RX RSSI of the received radio signal and determine whether thecorresponding signal is the wireless LAN signal. When the receivedsignal is the wireless LAN signal having the BSS identifier informationaccording to various embodiments to be described below, the terminal mayextract the BSS identifier information from the corresponding signal anddetermine whether the extracted BSS identifier information is the sameas the BSS identifier information of the corresponding terminal.

First, according to the embodiment of FIG. 8, the CCA threshold for thecorresponding signal may be decided based on whether the received radiosignal is the wireless LAN signal having the BSS identifier informationwhich is the same as the BSS identifier information of the terminal. Inthe embodiment of the present invention, the BSS identifier informationof the terminal is BSS identifier information allocated to thecorresponding terminal and may represent, when the correspondingterminal is a non-AP STA, BSS identifier information of an AP which thecorresponding terminal is associated with or intends to be associatedwith. In this case, the terminal may receive the BSS identifierinformation from the AP and the received BSS identifier information maybe stored in the corresponding terminal.

Referring to FIG. 8, when a received radio signal of a specific channelis the wireless LAN signal having an RX RSSI of the RX sensitivity 50 ormore and the CCA-SD threshold 30 or less, whether the channel is busy isdetermined based on whether the corresponding signal is the wireless LANsignal having the same BSS identifier information as that of theterminal. When the BSS identifier information extracted from the radiosignal is different from the BSS identifier information of the terminal(that is, in the case of OBSS wireless LAN signal 452), it is determinedthat the corresponding channel is in the idle state. However, when theBSS identifier information extracted from the radio signal is the sameas the BSS identifier information of the terminal (that is, in the caseof MYBSS wireless LAN signal 454), it is determined that thecorresponding channel is in the busy state.

Meanwhile, when the received radio signal of the specific channel is awireless LAN signal 430 having the RX RSSI between the CCA-SD threshold30 and the CCA-ED threshold 10, it is determined that the correspondingchannel is in the busy state. In this case, even in the case where thecorresponding signal is a wireless LAN signal having different BSSidentifier information from that of the terminal in addition to the casewhere the corresponding signal is the wireless LAN signal having thesame BSS identifier information as that of the terminal, the terminalthat receives the wireless LAN signal 430 determines that the channelwhere the corresponding signal is received is in the busy state.

During the energy detection process, when the radio signal of thespecific channel, which is received by the terminal is a radio signal410 having the RX RSSI of the CCA-ED threshold 10 or more, it isdetermined that the corresponding channel is in the busy state. Asdescribed above, in case that another type of radio signal (other thanthe wireless LAN signal) is received as well, the terminal determinesthat the corresponding channel is in the busy state, if the RX RSSI ofthe radio signal is the CCA-ED threshold 10 or more.

As such, according to the embodiment of FIG. 8, the CCA thresholdapplied to the wireless LAN signal having the same BSS identifierinformation as that of the terminal may have a different level from theCCA threshold applied to the wireless LAN signal having the differentBSS identifier information from that of the terminal. According to anembodiment, the CCA threshold applied to the wireless LAN signal havingthe different BSS identifier information from that of the terminal isset to a higher level than the CCA threshold applied to the wireless LANsignal having the same BSS identifier information as that of theterminal. According to the embodiment of FIG. 8, as the CCA thresholdfor the wireless LAN signal having the different BSS identifierinformation from that of the terminal, the predetermined CCA-SDthreshold 30 may be adopted and as the CCA threshold for the wirelessLAN signal having the same BSS identifier information as that of theterminal, the level of the RX sensitivity 50 of the terminal may beadopted.

FIGS. 9 and 10 illustrate another embodiment of the CCA method using theBSS identifier information. In the embodiments of FIGS. 9 and 10,duplicative description of parts, which are the same as or correspond tothe embodiment of FIG. 8, will be omitted.

First, according to the embodiment of FIG. 9, the CCA threshold for thecorresponding signal may be decided based on whether the received radiosignal is the wireless LAN signal having the BSS identifier informationwhich is the same as the BSS identifier information of the terminal.

Referring to FIG. 9, when the RX RSSI of a received radio signal of aspecific channel is the RX sensitivity 50 or more and a first CCA-SDthreshold 40 or less, it is determined that the corresponding channel isin the idle state. In this case, both in the case where the receivedsignal is a wireless LAN signal 454 having the same BSS identifierinformation as that of the terminal and in the case where the receivedsignal is a wireless LAN signal 452 having the different BSS identifierinformation from that of the terminal, the terminal determines that thechannel where the corresponding signal is received is in the idle state.

However, when the received radio signal of the specific channel is thewireless LAN signal having the RX RSSI between the first CCA-SDthreshold 40 and a second CCA-SD threshold 20, whether the channel isbusy is determined based on whether the corresponding signal is thewireless LAN signal having the same BSS identifier information as thatof the terminal. When the BSS identifier information extracted from theradio signal is different from the BSS identifier information of theterminal (that is, in the case of OBSS wireless LAN signal 442), it isdetermined that the corresponding channel is in the idle state. However,when the BSS identifier information extracted from the radio signal isthe same as the BSS identifier information of the terminal (that is, inthe case of MYBSS wireless LAN signal 444), it is determined that thecorresponding channel is in the busy state. In the embodiment of FIG. 9,the second CCA-SD threshold 20 which is used to perform the signaldetection for the wireless LAN signal having the different BSSidentifier information from that of the terminal may be set to a levelwhich is larger than the first CCA-SD threshold 40 and equal to orsmaller than the CCA-ED threshold.

Meanwhile, when the received radio signal of the specific channel is awireless LAN signal 420 having an RX RSSI between the second CCA-SDthreshold 20 and the CCA-ED threshold 10, it is determined that thecorresponding channel is in the busy state. In this case, even in thecase where the corresponding signal is a wireless LAN signal havingdifferent BSS identifier information from that of the terminal inaddition to the case where the corresponding signal is the wireless LANsignal having the same BSS identifier information as that of theterminal, the terminal that receives the wireless LAN signal 420determines that the channel where the corresponding signal is receivedis in the busy state.

During the energy detection process, when the received radio signal ofthe specific channel by the terminal is a radio signal 410 having the RXRSSI of the CCA-ED threshold 10 or more, it is determined that thecorresponding channel is in the busy state. As described above, in casethat another type of radio signal (other than the wireless LAN signal)is received as well, the terminal determines that the correspondingchannel is in the busy state, if the RX RSSI of the radio signal is theCCA-ED threshold 10 or more.

As such, according to the embodiment of FIG. 9, the CCA thresholdapplied to the wireless LAN signal having the same BSS identifierinformation as that of the terminal may have a different level from theCCA threshold applied to the wireless LAN signal having the differentBSS identifier information from that of the terminal. That is, as theCCA threshold for the wireless LAN signal having the same BSS identifierinformation as that of the terminal, the predetermined first CCA-SDthreshold 40 may be adopted and as the CCA threshold for the wirelessLAN signal having the different BSS identifier information from that ofthe terminal, the predetermined second CCA-SD threshold 20 may beadopted. Herein, the second CCA-SD threshold 20 may be set to a levelwhich is higher than the first CCA-SD threshold 40 and equal to or lowerthan the CCA-ED threshold.

Next, according to the embodiment of FIG. 10, when the RX RSSI of areceived radio signal of a specific channel is the RX sensitivity 50 ormore, the signal detection may be performed based on whether thecorresponding signal is the wireless LAN signal having the same BSSidentifier information as that of the terminal.

During the signal detection process, when the RX RSSI of the radiosignal received by the terminal is the RX sensitivity 50 or more and theradio signal is a wireless LAN signal 453 having the same BSS identifierinformation as that of the terminal, it is determined that thecorresponding channel is in the busy state. However, when the RX RSSI ofthe received radio signal is the RX sensitivity 50 or more and the radiosignal is a wireless LAN signal 451 having different BSS identifierinformation from that of the terminal, it is determined that thecorresponding channel is in the idle state.

Meanwhile, during the energy detection process, when the radio signalreceived by the terminal is the radio signal 410 having the RX RSSI ofthe CCA-ED threshold 10 or more, it is determined that the correspondingchannel is in the busy state. The terminal determines that thecorresponding channel is in the busy state regardless of whether thecorresponding signal is the wireless LAN signal having the same BSSidentifier information as that of the terminal and furthermore,regardless of whether the corresponding signal is the wireless LANsignal. Therefore, when the wireless LAN signal having the different BSSidentifier information from that of the terminal is received at a levelhigher than the CCA-ED threshold 10, it is determined that thecorresponding channel is in the busy state by the energy detectionprocess.

As such, according to the embodiment of FIG. 10, the terminal maydetermine whether the channel is busy based on whether the receivedradio signal is the wireless LAN signal having the same BSS identifierinformation as that of the terminal without using a separately setCCA-SD threshold during the signal detection process. However, theterminal may avoid a collision with the wireless LAN signal having thedifferent BSS identifier information from that of the terminal by usingthe predetermined CCA-ED threshold 10 for the energy detection.

FIGS. 11 to 13 are diagrams illustrating yet another embodiment of a CCAmethod using whether to obtain non-legacy wireless LAN information andBSS identifier information. In each embodiment of FIGS. 11 to 13, theterminal may measure the RX RSSI of the received radio signal anddetermine whether the corresponding signal is the wireless LAN signal.When the received signal is the wireless LAN signal having the BSSidentifier information according to various embodiments to be describedbelow, the terminal may extract the BSS identifier information from thecorresponding signal and determine whether the extracted BSS identifierinformation is the same as the BSS identifier information of thecorresponding terminal.

Moreover, the terminal may obtain at least one of the legacy wirelessLAN information and the non-legacy wireless LAN information from thereceived radio signal. As a result, the terminal may determine whetherthe received radio signal is a signal including only the legacy wirelessLAN information or a signal including both the legacy wireless LANinformation and the non-legacy wireless LAN information. According to anembodiment, the terminal may obtain at least one of the legacy wirelessLAN information and the non-legacy wireless LAN information by usingpreamble information of the received radio signal. The BSS identifierinformation of the radio signal may be extracted from the non-legacywireless LAN information when the non-legacy wireless LAN information isobtained from the corresponding signal. However, the present inventionis not limited thereto and according to various embodiments describedbelow the BSS identifier information of the radio signal may be alsoextracted from the legacy wireless LAN information. According to anembodiment of the present invention, the BSS identifier informationwhich is referred to for executing the CCA is included in the non-legacywireless LAN information, while the non-legacy wireless LAN informationmay not be included in the received radio signal. That is, when thereceived radio signal does not include the BSS identifier informationwhich is referred to for executing the CCA according to the embodimentof the present invention, the BSS identifier information may not beextracted from the corresponding signal. In this case, the BSSidentifier information of the corresponding signal for executing the CCAmay be set to a predetermined value. In the embodiments of FIGS. 11 to13, duplicative description of parts, which are the same as orcorrespond to the aforementioned embodiments, will be omitted.

First, referring to FIG. 11, when a received radio signal of a specificchannel is the wireless LAN signal having the RX RSSI of the RXsensitivity 50 or more and the first CCA-SD threshold 40 or less,whether the channel is busy is determined based on whether thecorresponding signal is the wireless LAN signal having the same BSSidentifier information as that of the terminal.

When the BSS identifier information extracted from the radio signal isdifferent from the BSS identifier information of the terminal (that is,in the case of OBSS wireless LAN signal), it is determined that thecorresponding channel is in the idle state. In this case, the OBSSwireless LAN signal 552 may be divided into an OBSS non-legacy wirelessLAN signal in which the non-legacy wireless LAN information may beobtained from the corresponding signal and an OBSS legacy wireless LANsignal in which the non-legacy wireless LAN information is not obtainedfrom the corresponding signal. The terminal determines that thecorresponding channel is in the idle state both in the case where theOBSS non-legacy wireless LAN signal is received and in the case wherethe OBSS legacy wireless LAN signal is received.

On the contrary, when the BSS identifier information extracted from theradio signal is the same as the BSS identifier information of theterminal (that is, in the case of MYBSS wireless LAN signal), it isdetermined that the corresponding channel is in the busy state.Similarly, the MYBSS wireless signal may be divided into a MYBSSnon-legacy wireless LAN signal 558 in which the non-legacy wireless LANinformation may be obtained from the corresponding signal and an MYBSSlegacy wireless LAN signal 556 in which the non-legacy wireless LANinformation is not obtained from the corresponding signal. The terminaldetermines that the corresponding channel is in the busy state both inthe case where the MYBSS non-legacy wireless LAN signal 558 is receivedand in the case where the MYBSS legacy wireless LAN signal 556 isreceived.

Meanwhile, when the received radio signal of the specific channel is thewireless LAN signal having the RX RSSI between the first CCA-SDthreshold 40 and the second CCA-SD threshold 20, whether the channel isbusy is determined based on whether the corresponding signal includesthe non-legacy wireless LAN information and whether the correspondingsignal has the same BSS identifier information as that of the terminal.According to an embodiment, the first CCA-SD threshold 40 may be set tothe same level as the CCA-SD threshold applied to the legacy terminaland the second CCA-SD threshold 20 may be set to a level higher than thefirst CCA-SD threshold 40 and equal to or lower than the CCA-EDthreshold.

When the non-legacy wireless LAN information is obtained from the radiosignal and the BSS identifier information of the corresponding signal isdifferent from the BSS identifier information of the terminal (that is,in the case of non-legacy OBSS signal 542), it is determined that thecorresponding channel is in the idle state. However, in other cases,when the non-legacy wireless LAN information is not obtained from theradio signal (that is, a legacy signal) or the BSS identifierinformation of the corresponding signal is the same as the BSSidentifier information of the terminal (that is, a MYBSS signal), it isdetermined that the corresponding channel is in the busy state. In moredetail, the case where it is determined that the channel is in the busystate includes i) a case where the non-legacy wireless LAN informationis not obtained from the radio signal and the BSS identifier informationof the corresponding signal is different from the BSS identifierinformation of the terminal (that is, in the case of legacy OBSS signal544), ii) a case where the non-legacy wireless LAN information is notobtained from the radio signal and the BSS identifier information of thecorresponding signal is the same as the BSS identifier information ofthe terminal (that is, in the case of legacy MYBSS signal 546), and iii)a case where the non-legacy wireless LAN information is obtained fromthe radio signal and the BSS identifier information of the correspondingsignal is the same as the BSS identifier information of the terminal(that is, in the case of non-legacy MYBSS signal 548).

That is, when the non-legacy wireless LAN information is not obtainedfrom the radio signal, it is determined that the corresponding channelis in the busy state, but when the non-legacy wireless LAN informationis obtained from the radio signal, whether the channel is busy isdetermined based on whether the BSS identifier information of thecorresponding signal is the same as the BSS identifier information ofthe terminal. Therefore, according to the embodiment of the presentinvention, when the non-legacy wireless LAN information is obtained fromthe radio signal, whether the corresponding channel is busy may bedetermined based on the BSS identifier information of the radio signal.According to an embodiment, when the non-legacy wireless LAN informationis not obtained from the radio signal, the BSS identifier informationwhich is referred to for executing the CCA of the present invention maynot be extracted from the corresponding signal. In this case, theterminal may determine that the channel is in the busy state regardlessof whether the BSS identifier information is extracted from thecorresponding signal.

The signal detection process may be performed by referring to thepreamble of the received radio signal. According to an embodiment, whenit is determined that the channel is in the busy state during the signaldetection process, even though the RX RSSI decreases to the first CCA-SDthreshold 40 or less while receiving the radio signal which is beingprotected, the terminal may not access the channel during a frametransmission time of the radio signal.

Meanwhile, when the received radio signal of the specific channel is awireless LAN signal 520 between the second CCA-SD threshold 20 and theCCA-ED threshold 10, it is determined that the corresponding channel isin the busy state. In this case, the terminal that receives the wirelessLAN signal 520 determines that a channel where the corresponding signalis received is in the busy state regardless of whether the non-legacywireless LAN information is obtained from the corresponding signal andfurthermore, regardless of whether the corresponding signal is thewireless LAN signal having the same BSS identifier information as thatof the terminal.

During the energy detection process, when the received radio signal ofthe specific channel by the terminal is a radio signal 510 of the CCA-EDthreshold 10 or more, it is determined that the corresponding channel isin the busy state. As described above, in case that another type ofradio signal (other than the wireless LAN signal) is received as well,the terminal determines that the corresponding channel is in the busystate, if the RX RSSI of the radio signal is the CCA-ED threshold 10 ormore.

Next, according to the embodiment of FIG. 12, when a received radiosignal of a specific channel is the wireless LAN signal having the RXsensitivity 50 or more and the RX RSSI of the first CCA-SD threshold 40or less, whether the channel is busy is determined based on whether thecorresponding signal includes the non-legacy wireless LAN informationand whether the corresponding signal has the same BSS identifierinformation as that of the terminal.

When the non-legacy wireless LAN information is obtained from the radiosignal and the BSS identifier information of the corresponding signal isthe same as the BSS identifier information of the terminal (that is, inthe case of non-legacy MYBSS signal 558), it is determined that thecorresponding channel is in the busy state. However, in other cases,when the BSS identifier information of the radio signal is differentfrom the BSS identifier information of the terminal (that is, OBSSsignal) or the non-legacy wireless LAN information is not obtained fromthe corresponding signal (that is, legacy signal), it is determined thatthe corresponding channel is in the idle state. In more detail, the casewhere it is determined that the channel is in the idle state includes i)a case where the non-legacy wireless LAN information is obtained fromthe radio signal and the BSS identifier information of the correspondingsignal is different from the BSS identifier information of the terminal(that is, in the case of non-legacy OBSS signal 552), ii) a case wherethe non-legacy wireless LAN information is not obtained from the radiosignal and the BSS identifier information of the corresponding signal isdifferent from the BSS identifier information of the terminal (that is,in the case of legacy BSS signal 554), and iii) a case where thenon-legacy wireless LAN information is not obtained from the radiosignal and the BSS identifier information of the corresponding signal isthe same as the BSS identifier information of the terminal (that is, inthe case of legacy MYBSS signal 556).

That is, when the non-legacy wireless LAN information is not obtainedfrom the radio signal, it is determined that the corresponding channelis in the idle state, but when the non-legacy wireless LAN informationis obtained from the radio signal, whether the channel is busy isdetermined based on whether the BSS identifier information of thecorresponding signal is the same as the BSS identifier information ofthe terminal. According to the embodiment of FIG. 12, when thenon-legacy wireless LAN information is obtained from the radio signaland the BSS identifier information of the corresponding signal isdifferent from the BSS identifier information of the terminal, apredetermined CCA threshold 20 may be used for the CCA of thecorresponding channel. However, when the non-legacy wireless LANinformation is obtained from the radio signal and the BSS identifierinformation of the corresponding signal is the same as the BSSidentifier information of the terminal, in the case where thecorresponding signal has the RX RSSI of the RX sensitivity 50 or more,it may be determined that the corresponding channel is in the busy statewithout setting a separate CCA threshold. According to an embodiment,when the non-legacy wireless LAN information is not obtained from theradio signal, the BSS identifier information which is referred to forexecuting the CCA of the present invention may not be extracted from thecorresponding signal. In this case, the terminal may determine that thechannel is in the idle state regardless of whether the BSS identifierinformation is extracted from the corresponding signal.

According to the embodiment of FIG. 12, even though the BSS identifierinformation which is referred to for executing the CCA is included inthe non-legacy wireless LAN information and the received wireless LANsignal does not include the non-legacy wireless LAN information, the CCAmay be efficiently executed. That is, when the received radio signal isthe legacy wireless LAN signal from which the BSS identifier informationis not extracted, it is determined that the corresponding channel is inthe idle state or the busy state in a lump according to the RX RSSI ofthe corresponding signal to minimize a time delay required to determinewhether the BSS identifier of the legacy wireless LAN signal is actuallythe same as the BSS identifier of the terminal. That is, only when thereceived radio signal is the non-legacy wireless LAN signal, theterminal additionally verifies the BSS identifier information todetermine whether the channel is in the idle/busy state.

Next, according to the embodiment of FIG. 13, when the RX RSSI of areceived radio signal of a specific channel is the RX sensitivity 50 ormore and the first CCA-SD threshold 40 or less, it is determined thatthe corresponding channel is in the idle state. In this case, theterminal determines that the corresponding channel is in the idle stateregardless of whether the received signal includes the non-legacywireless LAN information and whether the received signal has the sameBSS identifier information as that of the terminal. Further, accordingto the embodiment of FIG. 13, when the non-legacy wireless LANinformation is obtained from the radio signal and the BSS identifierinformation of the corresponding signal is the same as the BSSidentifier information of the terminal, a first CCA threshold may beused for the CCA of the corresponding channel. However, when thenon-legacy wireless LAN information is obtained from the radio signaland the BSS identifier information of the corresponding signal isdifferent from the BSS identifier information of the terminal, a secondCCA threshold having a higher level than the first CCA threshold may beused for the CCA of the corresponding channel.

According to the embodiment of FIG. 13, when the wireless LAN signalhaving the same BSS identifier information as that of the terminal isreceived, a problem of unfairness in that different CCA thresholds areapplied according to whether the corresponding wireless LAN signalincludes the non-legacy wireless LAN information may be resolved. Thatis, CCA thresholds for the legacy MYBSS signal and the non-legacy MYBSSsignal are similarly applied to maintain fairness for channel occupationbetween a legacy terminal and a non-legacy terminal.

Meanwhile, in the embodiments of FIGS. 12 and 13, when the radio signalhaving the RX RSSI of the first CCA-SD threshold 40 or more is received,a CCA process may be performed similarly to the embodiment of FIG. 11.

FIG. 14 is a diagram illustrating a frame structure of a wireless LANsignal according to an embodiment of the present invention. Referring toFIG. 14, the wireless LAN signal according to the embodiment of thepresent invention may include a legacy preamble 710 for a legacyterminal (e.g. a terminal such as 802.11a/g, or the like) and anon-legacy preamble 720 for a non-legacy terminal (e.g. a terminal of802.11ax). First, the legacy preamble 710 may include legacy wirelessLAN information which the legacy terminal is able to decode, forinstance, L-STF, L-LTF, L-SIG fields, and the like. Next, the non-legacypreamble 720 may include non-legacy wireless LAN information which onlythe non-legacy terminal is able to decode and the non-legacy wirelessLAN information may not be decoded by the legacy terminal. Meanwhile,the legacy preamble 710 may include at least some of the non-legacywireless LAN information which the non-legacy terminal is able to decodeaccording to the embodiment. Moreover, the non-legacy preamble 720 mayinclude at least one field of the legacy preamble 710, for instance,repeated information of a part or the entirety of the L-SIG field.

According to an embodiment of the present invention, the BSS identifierinformation which is referred to for executing the CCA may be includedin the non-legacy preamble 720 as the non-legacy wireless LANinformation. In this case, the BSS identifier information may beextracted from a predetermined bit filed of the non-legacy preamble 720.Meanwhile, according to another embodiment of the present invention, theBSS identifier information may be extracted from additional informationof the legacy preamble 710. For example, the legacy preamble 710 mayinclude the non-legacy wireless LAN information through an additionalsubcarrier set, and the like as described below and the BSS identifierinformation may be obtained from the non-legacy wireless LAN informationincluded in the legacy preamble 710. According to yet another embodimentof the present invention, the BSS identifier information may beextracted from a predetermined bit field of the legacy preamble 710. Inthis case, the predetermined bit field of the legacy preamble 710 may bea bit field set for the legacy terminal and a value of the correspondingbit field may be used as the BSS identifier information under a specificcondition as described below.

FIG. 15 illustrates a method for representing the BSS identifierinformation according to an embodiment of the present invention.According to the embodiment of the present invention, the BSS identifierinformation may be represented as a predetermined bit filed of thenon-legacy preamble 720 of FIG. 14. According to an embodiment of thepresent invention, the BSS identifier information may be abbreviatedinformation of a BSS identifier allocated to each BSS and may beinformation having smaller bits than the actual BSS identifier. Forexample, when the BSS identifier is represented as information of 24bits in a specific wireless LAN system, the BSS identifier informationmay be represented as a bit filed having a predetermined length in therange of 1 bit to 23 bits. In the preset invention, the BSS identifierinformation is information acquired by classifying the actual BSSidentifier into a predetermined category and may be named even as a BSScolor. A method for obtaining a BSS color abbreviated from the BSSidentifier includes a method using a combination of bit values at apredetermined location of the BSS identifier, a method using a resultvalue acquired by applying a predetermined Hash function to the BSSidentifier, and the like.

FIG. 15 as an embodiment thereof illustrates a result of acquiring theBSS color by using last 3 bit values of the BSS identifier. As such, theBSS color may be included in the preamble of the wireless LAN signal asinformation of a smaller amount than the actual BSS identifier, and as aresult, each terminal may efficiently determine whether the receivedwireless LAN signal is a signal having the same BSS identifier as thecorresponding terminal within a short time. The BSS identifierinformation may be represented as a predetermined bit of the non-legacypreamble.

Meanwhile, according to an embodiment of the present invention, thenon-legacy preamble 720 may include the repeated L-SIG field and therepeated L-SIG field may be configured to have at least the some bitsidentical with the L-SIG field of the legacy preamble 710. In this case,the bits different from the L-SIG field of the legacy preamble 710 amongthe bits of the repeated L-SIG field may represent the BSS identifierinformation, bandwidth information of the system, non-legacy wirelessLAN system information, channel information, and the like.

According to an additional embodiment of the present invention,additional information may be transmitted through a modulation methodapplied to the repeated L-SIG field. That is, the repeated L-SIG fieldmay be represented as the same modulation value as the L-SIG field ofthe legacy preamble 710 or otherwise expressed as a counter modulationvalue. Herein, the counter modulation value may be represented through aphase shift between modulation symbols transmitted to the L-SIG of thelegacy preamble 710 and modulation symbols of the repeated L-SIG and theadditional information may be transmitted through a phase shift amount.In detail, when the L-SIG of the legacy preamble 710 and the repeatedL-SIG are multiplied by (1, 1) to be transmitted, the symbols of bothfields have the same phase and when the L-SIG of the legacy preamble 710and the repeated L-SIG are multiplied by (1, −1) to be transmitted, aphase shift of 180° occurs between the symbols of the repeated L-SIG andthe symbols of the legacy preamble 710. In this case, specific flaginformation for the non-legacy wireless LAN information may bedetermined according to whether the repeated L-SIG field is representedas the same modulation value as the L-SIG field of the legacy preamble710, for example, whether a SIG-A field of the non-legacy preamble has avariable length, whether a SIG-B field is included in the non-legacypreamble, whether a specific bit field of the non-legacy preamble(alternatively, legacy preamble) represents the BSS identifierinformation, and the like may be determined.

FIGS. 16 and 17 as another embodiment of the present inventionillustrate a method for obtaining the non-legacy wireless LANinformation by using an additional subcarrier set of the wireless LANsignal.

First, FIG. 16 illustrates an embodiment of a subcarrier configurationused in the legacy preamble of the wireless LAN signal. According to anembodiment of the present invention, the subcarrier set of the legacypreamble of the non-legacy wireless LAN signal may be configuredequivalent to the subcarrier set of the legacy wireless LAN signal. Thatis, the subcarrier set of the legacy preamble may be constituted by atotal of 52 subcarrier including 4 pilot subcarriers and 48 datasubcarriers in a bandwidth of 20 MHz. In this case, when numbers ofrespective subcarriers are set to −26, −25, . . . , −2, −1, 1, 2, . . ., 25, and 26, subcarriers having numbers of −21, −7, 7, and 21 are usedas the pilot subcarriers and subcarriers of the residual numbers areused as the data subcarriers. Such a basic configuration of thesubcarrier is required to maintain mutual compatibility in anenvironment in which the legacy wireless LAN system (e.g. 802.11a/g) andthe non-legacy wireless LAN system (e.g. 802.11 ax, or the like)coexist. That is, the legacy preamble of the non-legacy wireless LANsignal as well as the legacy wireless LAN signal has the subcarrierconfiguration illustrated in FIG. 16 to provide backward compatibilityto the legacy terminal.

FIG. 17 illustrates an embodiment of the subcarrier configuration usedin the non-legacy wireless LAN signal. An additional subcarrier may beused without interference of an adjacent bandwidth in the non-legacywireless LAN system with the development of a filter or an amplifierused in the terminal. Referring to FIG. 17, the subcarrier of thenon-legacy wireless LAN signal according to the embodiment of thepresent invention may be configured to include a first subcarrier set800 and a second subcarrier set 820. In more detail, the firstsubcarrier set 800 may be configured equivalent to the subcarrier set ofthe legacy wireless LAN signal illustrated in FIG. 16. Further, thesecond subcarrier set 820 as a subcarrier set different from the firstsubcarrier set 800 may include 4 extra subcarriers, two at each higherand lower indices of the first subcarrier set 800, according to anembodiment. According to the embodiment of FIG. 17, since the non-legacywireless LAN signal uses pilot subcarriers at the same location and ofthe same number as the legacy wireless LAN signal, 52 data subcarrierswhich increase from the existing 48 subcarriers by 4 may be used.According to an embodiment, the subcarrier configuration may be usedafter a legacy preamble part of the non-legacy wireless LAN signal. Thenon-legacy terminal may obtain information through a total of 56subcarriers in the respective non-legacy preamble and data field of thereceived non-legacy wireless LAN signal.

According to the embodiment of the present invention, the secondsubcarrier set 820 included in the non-legacy preamble may represent theBSS identifier information, the bandwidth information of the system, thenon-legacy wireless LAN system information, the channel information, andthe like. In this case, a separate parity bit for parity check of thesecond subcarrier set 820 may be included in the non-legacy preamble.According to an embodiment, when the non-legacy preamble includes therepeated L-SIG field as described above, the BSS identifier information,the bandwidth information of the system, the non-legacy wireless LANsystem information, the channel information, and the like may berepresented through the second subcarrier set 820 of the repeated L-SIGfield.

Meanwhile, according to another embodiment of the present invention, thesubcarrier configuration of FIG. 17 may be extensively applied to thelegacy preamble of the non-legacy wireless LAN signal. That is, thelegacy preamble of the non-legacy wireless LAN signal may additionallyinclude the second subcarrier set 820 and transfer the non-legacywireless LAN information through the second subcarrier set 820. In thiscase, the legacy terminal may not obtain information from the secondsubcarrier set 820, but the non-legacy terminal may obtain additionalinformation from the second subcarrier set 820 of the legacy preamble.

For example, when it is assumed that the second subcarrier set 820additionally used in the legacy preamble includes 4 subcarriers, theindices (that is, subcarrier numbers) of the corresponding subcarriersmay be set to −28, −27, 27, and 28, respectively as illustrated in FIG.17. In this case, when a BPSK modulation scheme is used in the legacypreamble and the same modulation scheme is applied to the secondsubcarrier set, information of a total of 4 bits may be additionallytransmitted. Similarly, when a QPSK modulation scheme is applied to thesecond subcarrier set, information of a total of 8 bits may beadditionally transmitted. In this case, the parity bit for parity checkof the second subcarrier set included in the legacy preamble may beincluded in the non-legacy preamble.

According to an additional embodiment of the present invention, onlysome of total bits which may be represented by the second subcarrier set820 of the legacy preamble may be used for transmitting the additionalinformation. For example, only some bits of the second subcarrier set820 may be used for transmitting the additional information forcompatibility with the parity check of the legacy preamble. That is, theinformation added to the second subcarrier set 820 may be configured tohave even parities for compatibility with the parity bit used in theexisting L-SIG and when the BPSK modulation scheme is used, informationwhich may be transferred through the second subcarrier set 820 may beinformation of a total of 3 bits such as 1010, 0101, 1100, 0011, 1001,0110, 1111, and 0000.

According to another embodiment, a specific bit of the second subcarrierset 820 may be used as the parity check bit and the residual bits may beused for transmitting the additional information. For example, 3 bitsamong 4 bits of the second subcarrier set 820 may be used fortransmitting the additional information and 1 bit may be used as theparity bit. In this case, the parity bit of the second subcarrier set820 may be used for the parity check for bits added by the secondsubcarrier set 820 or otherwise used for parity check of the entireL-SIG including the second subcarrier set 820. In this case, the paritycheck with respect to the legacy wireless LAN signal may be performed byusing the existing parity bit of the L-SIG and the parity check withrespect to the non-legacy wireless LAN signal is performed by using boththe existing parity bit of the L-SIG and the parity bit of the secondsubcarrier set 820 to achieve parity check with higher-reliability.According to yet another embodiment, the parity check with respect tothe non-legacy wireless LAN information added by the second subcarrierset 820 may be performed by using a reserved bit of the L-SIG.

When the additional information for the non-legacy terminal istransmitted through the second subcarrier set 820 of the legacypreamble, the non-legacy terminal may more rapidly obtain the additionalinformation in the legacy preamble of the received wireless LAN signal,thus an initial access delay or detection of a preamble, a header, and apacket which are not required may be reduced by using the obtainedadditional information. Further, according to the embodiment of thepresent invention, the non-legacy terminal may obtain the non-legacywireless LAN information from the second subcarrier set 820 of thelegacy preamble and the non-legacy wireless LAN information obtained inthat case may include the BSS identifier information, the bandwidthinformation of the system, the non-legacy wireless LAN systeminformation, the channel information, and the like. When the non-legacyterminal obtains the second subcarrier set 820 in the legacy preamble ofthe received wireless LAN signal, the non-legacy terminal may recognizethat the corresponding wireless LAN signal includes the non-legacywireless LAN information.

In the embodiment of FIG. 17, the embodiment in which 4 additional datasubcarriers are included in the second subcarrier set 820 is described,but the present invention is not limited thereto and different numbersof subcarriers may be included in a second subcarrier set 820. Further,the embodiment of FIG. 17 may be applied to a case where otherbandwidths including 40 MHz, 80 MHz, and 160 MHz are used as well as acase where a bandwidth of the wireless LAN signal is 20 MHz.

FIG. 18 as yet another embodiment illustrates a method for representingthe non-legacy wireless LAN information by using a predetermined bitfield of the legacy preamble.

According to an additional embodiment of the present invention, thenon-legacy wireless LAN information may be extracted from thepredetermined bit field of the legacy preamble under a specificcondition. FIG. 18 as an embodiment thereof illustrates a rate bit fieldincluded in the L-SIG of the legacy preamble. As illustrated in FIG. 18,a 4-th bit in the rate bit filed of the existing legacy preamble iscontinuously set to 1. Therefore, information on a data rate, amodulation scheme, and a coding rate of the legacy wireless LAN signalmay be obtained through former 3 bit values in the rate bit field.Accordingly, according to the embodiment of the present invention,whether the corresponding rate bit field represents the non-legacywireless LAN information may be decided based on the 4-th bit value ofthe rate bit field. That is, when the 4-th bit of the rate bit field hasa value of 1, the corresponding rate bit field may represent theexisting information, that is, the data rate, the modulation scheme, andthe coding rate. However, when the 4-th bit of the rate bit field has avalue of 0, the corresponding rate bit field may represent thenon-legacy wireless LAN information.

When it is determined that the rate bit field includes the non-legacywireless LAN information, the BSS identifier information may beextracted from former 3 bit values of the corresponding rate bit fieldas illustrated in FIG. 18. However, the present invention is not limitedthereto and the non-legacy wireless LAN information such as bandwidthinformation, channel information, an association identifier (AID), andthe like of the non-legacy wireless LAN signal may be extracted from therate bit field. In this case, actual rate information for the non-legacyterminal may be transmitted through the non-legacy preamble. Meanwhile,even when the rate bit field includes the non-legacy wireless LANinformation, the legacy terminal may analyze the non-legacy wireless LANinformation as rate information. For such a situation, by appropriatelyconfiguring a length field of the L-SIG, the legacy terminals mayperform a transmission delay (NAV configuration, and the like) by usingL-SIG length information of other terminal packets when the transmissiondelay is required due to transmission of other terminals. In moredetail, since the length field of the legacy preamble represents thesize (the number of bytes) of transmission data, when information on thenumber of transmitted bits per OFDM symbol is obtained based on amodulation and coding scheme (MCS) and the length field is divided bythe obtained information, the number of required OFDM symbols isdetermined. In this case, the network allocation vector (NAV)configuration may be performed according to the obtained number of OFDMsymbols, and when the rate bit field is used as the non-legacy wirelessLAN information in accordance with the embodiment of the presentinvention, the NAV may be configured as large as a required length byadjusting the length field.

As such, according to the embodiment of the present invention, based oninformation on predetermined specific bits of the legacy preamble,whether the corresponding legacy preamble includes the non-legacywireless LAN information may be determined. When it is determined thatthe legacy preamble includes the non-legacy wireless LAN information,the non-legacy wireless LAN information such as the BSS identifierinformation, and the like may be extracted from the predetermined bitfield of the legacy preamble, for instance, the rate bit field.

Meanwhile, according to an additional embodiment of the presentinvention, information on more bits may be secured by using acombination of the second subcarrier set of the legacy preamble and thespecific bit field (that is, rate bit field), and as a result, thenon-legacy wireless LAN information may be transferred. For example,when the legacy preamble is configured to additionally include thesecond subcarrier set, the non-legacy terminal may determine that thecorresponding legacy preamble includes the non-legacy wireless LANinformation and extract the BSS identifier information from all or someof 4 bits in the rate bit field. Furthermore, when the legacy preambleis configured to additionally include the second subcarrier set, thenon-legacy terminal may analyze the entirety of the L-SIG bit field ofthe legacy preamble as the non-legacy wireless LAN information. As such,according to the embodiment of FIG. 18, since at least some ofnon-legacy wireless LAN information such as the BSS identifierinformation, and the like may be obtained from the legacy preamblebefore checking the non-legacy preamble, the CCA may be performed withina shorter time.

FIG. 19 is a diagram illustrating an embodiment of a method forperforming communication by additionally using BSS configurationinformation. According to the embodiment of the present invention theBSS configuration information may include at least one of channelinformation, bandwidth information and communication scheme informationused in the corresponding BSS.

As described above, even though different BSSs use the non-overlappingchannel, the adjacent channel interference may occur due to the use ofthe adjacent primary channel. In particular, when multiple BSSs coexistwith high density, each terminal may determine that the channel is busyat the time of executing the CCA due to accumulated interferenceamounts, and as a result, an operation of the BSS may be limited.Referring to FIG. 19, in BSS-1 operated by AP-1, STA-1 and STA-2 areassociated with AP-1 and at least a part of a communication coverage ofBSS-2 operated by AP-2 and a communication coverage of BSS-3 operated byAP-3 may overlap with the communication coverage of BSS-1. Further,BSS-1, BSS-2, and BSS-3 use a 20 MHz band of CH1, the 20 MHz band ofCH5, and a 40 MHz band of CH9, respectively. Although the respectiveBSSs of FIG. 19 use different channels, terminals of the respective BSSsusing the adjacent channel may interfere with each other. For example,when STA-1 performs the CCA for CH1 in order to transmit data to AP-1,adjacent channel interference in which the communication signal of BSS-2using CH5 is partially sensed may occur.

The adjacent channel interference may occur due to spurious of theadjacent channel signal and a channel of a frequency band which isfarther from a center frequency of the adjacent channel is lessinfluenced by spurious power. Moreover, the spurious may show differentaspects according to a frequency bandwidth used in the adjacent channelsignal. Therefore, in order to decide the CCA threshold for efficientwireless communication in the overlapping BSS environment, additionalinformation regarding a channel used in an adjacent BSS needs to beconsidered.

According to the embodiment of the present invention, each terminal maytransmit the BSS configuration information such as channel information,bandwidth information, communication scheme information, and the likeused by the corresponding BSS in company with the radio signal at thetime of transmitting the radio signal. When a plurality of channelsincluding the primary channel and the secondary channel are usedtogether in a specific BSS, information on all channels used in thecorresponding BSS may be included in the BSS configuration information.However, according to another embodiment, only information on theprimary channel among all channels which are being used may be includedin the BSS configuration information. Further, the bandwidth informationmay represent the entire bandwidth information used by a frame of thecorresponding signal or information on a minimum bandwidth which needsto be protected. According to an embodiment, when both the channelinformation and the bandwidth information are included in the BSSconfiguration information, the BSS configuration information may includethe primary channel information and the bandwidth information of thecorresponding BSS. The terminal that obtains the BSS configurationinformation may obtain information on all channels which are being usedin the corresponding BSS by using the primary channel information andthe bandwidth information.

Meanwhile, the communication scheme information may representinformation on a specific wireless LAN communication scheme, that is, acommunication scheme such as IEEE 802.11a/g/n/ac, Wi-fi Direct, and thelike. Moreover, the communication scheme information may includeinformation (e.g. the non-legacy wireless LAN information) to identifythe legacy wireless LAN signal and the non-legacy wireless LAN signaland furthermore, information to identify whether the correspondingsignal is the wireless LAN signal, information to identify acommunication scheme such as LTE, Bluetooth, or the like.

The BSS configuration information may be transmitted from the APoperating each BSS in an association step or otherwise included in thepreamble of the radio signal transmitted by each terminal. According toan embodiment of the present invention, the BSS configurationinformation may be included in the non-legacy wireless LAN informationof the radio signal and in more detail, as described in the embodimentof the BSS identifier information, the BSS configuration information maybe represented as the predetermined bit field of the non-legacypreamble, the additional subcarrier of the legacy preamble, and thelike. Moreover, according to another embodiment, the BSS configurationinformation may be represented in the form of the predetermined bitfield of the legacy preamble such as the rate bit field, or the like.The radio signal may include the BSS identifier information and the BSSconfiguration information as separate information, respectively andalternatively, may include only any one of the BSS identifierinformation and the BSS configuration information.

The terminal of the present invention extracts the BSS configurationinformation from the received radio signal and decides the CCA thresholdby using the extracted BSS configuration information. In more detail,the terminal adjusts the CCA threshold based on a result of comparingthe BSS configuration information extracted from the received radiosignal and the BSS configuration information of the BSS to which thecorresponding terminal belongs. In this case, the adjusted CCA thresholdmay be the CCA-SD threshold for the signal detection.

First, the terminal may set the CCA threshold when the channelinformation of the received radio signal is different from the channelinformation of the BSS to which the corresponding terminal belongs tohave a higher level than the CCA threshold when information on bothchannels is the same as each other. For example, when the channelinformation extracted from the received radio signal and the channelinformation of the BSS to which the terminal belongs are the same aseach other, the terminal may use a CCA threshold which is basically setwithout adjusting the CCA threshold. However, when the channelinformation extracted from the received radio signal and the channelinformation of the BSS to which the terminal belongs are different fromeach other, the terminal may regard the corresponding radio signal as asignal received by spurious and increase the CCA threshold. Further,even when the CCA threshold increases based on information other thanthe channel information, a CCA threshold increment amount when thechannel information is different may be larger than a CCA thresholdincrement amount when the channel information is the same.

According to the embodiment of the present invention, the terminal mayadjust the CCA threshold based on whether a busy channel of the receivedradio signal and a busy channel of the BSS to which the correspondingterminal belongs are adjacent to each other. Since the spuriousprimarily influences only the adjacent channel, the terminal may set theCCA threshold when the channel information of the received radio signaland the channel information of the BSS to which the correspondingterminal belongs represent that both channels are adjacent to each otherto have a higher level than the CCA threshold when the correspondingchannel information represents that both channels are not adjacent toeach other. For example, when the channel information of the receivedradio signal and the channel information of the BSS to which thecorresponding terminal belongs represent that both channels are adjacentchannels, the terminal may set the CCA threshold to be a larger valuethan the basically set CCA threshold. According to another embodiment,the terminal may increase the CCA threshold when the center frequency ofthe busy channel of the received radio signal and the center frequencyof the busy channel of the BSS to which the corresponding terminalbelongs are different from each other and decrease the CCA thresholdincrement amount as a distance between the center frequencies increases.

Further, the terminal may adjust the CCA threshold based on thebandwidth information of the received radio signal. The terminal mayincrease the CCA threshold when the channel information of the receivedradio signal and the channel information of the BSS to which thecorresponding terminal belongs are different from each other(alternatively, represent that both channels are adjacent channels) anddecrease the CCA threshold increment amount as the bandwidth of thereceived radio signal is larger. For example, the terminal may set theCCA threshold when the bandwidth information of the received radiosignal represents 20 MHz to a higher level than the CCA threshold whenthe corresponding bandwidth information represents 40 MHz, 80 MHz, or160 MHz. According to another embodiment, the terminal may increase theCCA threshold only when the bandwidth of the received radio signal isequal to or less than a predetermined bandwidth, for instance, 20 MHz or40 MHz. The terminal may adjust the CCA threshold based on the bandwidthinformation of the BSS to which the corresponding terminal belongs andwhen the corresponding BSS uses a large bandwidth over 20 MHz, theterminal may set the CCA threshold for the primary channel to a lowerlevel than the CCA threshold for the secondary channel.

Moreover, the terminal may adjust the CCA threshold based on thecommunication scheme information of the received radio signal. Althoughcommunication is performed by using the same channel, a CCA thresholdsetting criterion, a spectrum mask, and the like may vary depending onthe communication scheme. Accordingly, the terminal may set the CCAthreshold by considering a difference depending on the communicationscheme. According to an embodiment, the terminal may set the CCAthreshold when the received radio signal is the non-legacy wireless LANsignal to have a higher level than the CCA threshold when the receivedradio signal is the legacy wireless LAN signal. According to anotherembodiment, the CCA threshold when the received radio signal is a signalof communication scheme (e.g. LTE, Bluetooth, or the like) other thanthe wireless LAN may be set to a higher level than the CCA thresholdwhen the corresponding radio signal is the wireless LAN signal.According to an additional embodiment of the present invention, thecommunication scheme information may include provider information of thecorresponding communication and a CCA threshold for a radio signalhaving the same provider information as the corresponding terminal maybe set to a lower level than the CCA threshold for a radio signal havingdifferent provider information. By adjusting the CCA threshold asdescribed above, the terminal may provide higher protection for thelegacy wireless LAN signal than the non-legacy wireless LAN signal, thewireless LAN signal than the signal of another communication scheme, andthe radio signal having different provider information than the radiosignal having the same provider information, respectively. The terminaldetermines the CCA threshold by using a combination of one or more ofthe BSS configuration information. The terminal may perform the CCA forthe corresponding channel by using the determined CCA threshold.

Although the present invention is described by using the wireless LANcommunication as an example, the present invention is not limitedthereto and the present invention may be similarly applied even to othercommunication systems such as cellular communication, and the like.Further, the method, the apparatus, and the system of the presentinvention are described in association with the specific embodiments,but some or all of the components and operations of the presentinvention may be implemented by using a computer system having universalhardware architecture.

The detailed described embodiments of the present invention may beimplemented by various means. For example, the embodiments of thepresent invention may be implemented by a hardware, a firmware, asoftware, or a combination thereof.

In case of the hardware implementation, the method according to theembodiments of the present invention may be implemented by one or moreof Application Specific Integrated Circuits (ASICSs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, micro-controllers, micro-processors,and the like.

In case of the firmware implementation or the software implementation,the method according to the embodiments of the present invention may beimplemented by a module, a procedure, a function, or the like whichperforms the operations described above. Software codes may be stored ina memory and operated by a processor. The processor may be equipped withthe memory internally or externally and the memory may exchange datawith the processor by various publicly known means.

The description of the present invention is used for exemplification andthose skilled in the art will be able to understand that the presentinvention can be easily modified to other detailed forms withoutchanging the technical idea or an essential feature thereof. Thus, it isto be appreciated that the embodiments described above are intended tobe illustrative in every sense, and not restrictive. For example, eachcomponent described as a single type may be implemented to bedistributed and similarly, components described to be distributed mayalso be implemented in an associated form.

The scope of the present invention is represented by the claims to bedescribed below rather than the detailed description, and it is to beinterpreted that the meaning and scope of the claims and all the changesor modified forms derived from the equivalents thereof come within thescope of the present invention.

The invention claimed is:
 1. A wireless communication method of aterminal, comprising: receiving a radio signal of a specific channel;measuring a signal strength of the received radio signal; anddetermining whether the specific channel is busy based on the measuredsignal strength and BSS identifier information of the radio signal,wherein the determining is performed based on clear channel assessment(CCA) for the specific channel, and a CCA threshold used for the CCA isset by the terminal to different levels according to whether the BSSidentifier information of the radio signal is the same as BSS identifierinformation of the terminal, wherein when the BSS identifier informationof the radio signal is the same as BSS identifier information of theterminal, a first CCA threshold is used for the CCA, and when the BSSidentifier information of the radio signal is different from BSSidentifier information of the terminal, a second CCA threshold having ahigher level than the first CCA threshold is used for the CCA, andwherein when the BSS identifier information of the radio signal isdifferent from the BSS identifier information of the terminal and thesignal strength of the received radio signal is below the second CCAthreshold, the channel is determined to be idle.
 2. The wirelesscommunication method of claim 1, wherein the BSS identifier informationof the radio signal represents abbreviated information of a BSSidentifier for the radio signal.
 3. The wireless communication method ofclaim 1, further comprising: obtaining at least one of legacy wirelessLAN information and non-legacy wireless LAN information by usingpreamble information of the received radio signal, wherein in thedetermining, when the non-legacy wireless LAN information is obtainedfrom the radio signal, whether the specific channel is busy isdetermined based on the BSS identifier information of the radio signal.4. The wireless communication method of claim 3, wherein the radiosignal includes a first preamble for a legacy terminal and a secondpreamble for a non-legacy terminal, and the BSS identifier informationof the radio signal is extracted from the second preamble of the radiosignal.
 5. The wireless communication method of claim 3, wherein theradio signal includes a first preamble for the legacy terminal and asecond preamble for the non-legacy terminal and the first preamble isconfigured to at least include a first subcarrier set for the legacyterminal, and when the first preamble is configured to additionallyinclude a second subcarrier set different from the first subcarrier set,the non-legacy wireless LAN information is obtained from the secondsubcarrier set.
 6. The wireless communication method of claim 5, whereinthe BSS identifier information of the received radio signal is extractedfrom information on the second subcarrier set of the first preamble. 7.The wireless communication method of claim 3, wherein the radio signalincludes a first preamble for the legacy terminal and a second preamblefor the non-legacy terminal, and whether the radio signal includes thenon-legacy wireless LAN information is determined based on informationon predetermined bits of the first preamble.
 8. The wirelesscommunication method of claim 3, wherein the radio signal includes afirst preamble for the legacy terminal and a second preamble for thenon-legacy terminal, and the BSS identifier information of the radiosignal is extracted from a predetermined bit field of the firstpreamble.
 9. The wireless communication method of claim 8, wherein apredetermined bit of the predetermined bit field represents whether theradio signal includes the non-legacy wireless LAN information, and whenthe predetermined bit represents that the radio signal includes thenon-legacy wireless LAN information, the BSS identifier information ofthe radio signal is extracted from the predetermined bit field.
 10. Thewireless communication method of claim 8, wherein the first preamble isconfigured to at least include the first subcarrier set for the legacyterminal, and when the first preamble is configured to additionallyinclude the second subcarrier set different from the first subcarrierset, the BSS identifier information of the radio signal is extractedfrom the predetermined bit field.
 11. A wireless communication terminalcomprising: a transceiver transmitting and receiving a radio signal; anda processor controlling an operation of the terminal, wherein theprocessor is configured to: measure a signal strength of a radio signalof a specific channel, which is received through the transceiver, anddetermine whether the specific channel is busy based on the measuredsignal strength and BSS identifier information of the radio signal,perform the determination based on clear channel assessment (CCA) forthe specific channel, wherein a CCA threshold used for the CCA is set bythe terminal to different levels according to whether the BSS identifierinformation of the radio signal is the same as BSS identifierinformation of the terminal, wherein when the BSS identifier informationof the radio signal is the same as BSS identifier information of theterminal, a first CCA threshold is used for the CCA, and when the BSSidentifier information of the radio signal is different from BSSidentifier information of the terminal, a second CCA threshold having ahigher level than the first CCA threshold is used for the CCA, whereinwhen the BSS identifier information of the radio signal is differentfrom the BSS identifier information of the terminal and the signalstrength of the received radio signal is below the second CCA threshold,the channel is determined to be idle, and wherein the processor isfurther configured to: obtain at least one of legacy wireless LANinformation and non-legacy wireless LAN information by using preambleinformation of the received radio signal, and determine, when thenon-legacy wireless LAN information is obtained from the radio signal,whether the specific channel is busy based on the BSS identifierinformation of the radio signal.